The present invention relates to an actuator latch mechanism of a hard disk drive (HDD) for latching an actuator arm in place when external shock or vibration is applied to the HDD.
HDDs are widely used as auxiliary memory devices of computer systems because of their ability to rapidly access large amounts of data. In general, HDDs employ a read/write head to record data on a disk or reproduce data stored on the disk. The disk has a number of tracks, and the data is stored in bits on each track.
The data storage capacity of a typical disk, i.e., the number of TPI (tracks per inch) and BPI (bits per inch), has increased substantially in recent times. As a result, the fields in which HDDs are being used as memory devices have expanded. In particular, there is a growing demand for compact HDDs for portable electronic products such as laptops, personal digital assistants (PDAs), and mobile phones. Compact HDDs currently have a standard size of 2.5 inches (disk diameter). However, a compact 0.85 inch HDD has been developed for use in mobile phones or MP3 players.
In addition to a read/write head, an HDD typically includes a disk pack having a disk for recording data and a spindle motor for rotating the disk about an axis, a head stack assembly (HSA) having an actuator arm which carries the read/write head, a voice coil motor (VCM) for rotating the actuator arm to position the read/write head over the disk, and a base on which the abovementioned elements are installed.
The read/write head reads and writes data while floating at a predetermined height over a data area of the disk where the tracks are provided, and while the disk is rotating. When the HDD is not operated, that is, when the disk is stationary, the read/write head is parked at a position outside the data area of the disk to prevent the read/write head from colliding against the data area of the disk.
To this end, the HDD may employ a contact start stop (CSS) parking system or a ramp loading parking system. In the CSS parking system, an inner circumferential portion of the disk constitutes a parking zone in which data is not recorded, and the read/write head is parked in contact with the parking zone when the HDD is not in operation. In the ramp loading parking system, a ramp is disposed radially outwardly of the disk and an end tab is provided at a leading end portion of the actuator arm. The end tab is supported by the ramp when the read/write head may is parked.
However, a strong external shock or vibration applied to the HDD when the read/write head is parked may jar the actuator arm loose, causing the actuator arm to rotate to such an extent that the read/write head contacts the data area of the disk. In this case, the read/write head and/or the data area of the disk may be damaged. To prevent such a problem, a latch mechanism is provided to latch onto the actuator arm when the read/write head is parked and an excessive amount of shock or vibrations is applied to the HDD.
There are a variety of known types of latch mechanisms. One is a multi-pawl type of latch mechanism that includes a latch lever having several hooks at a leading end thereof, and a bobbin protrusion which extends from a rear end portion of the actuator arm. The latch lever is supported so as to be rotatable relative to the base, and is designed to latch onto the bobbin protrusion when the actuator arm is jarred loose from the state in which the read/write head is parked in an attempt to prevent the read/write head from moving onto the data area of the disk. Although the multi-pawl type of latch mechanism can keep the actuator arm latched when certain shocks are applied to the HDD, the actuator arm may nonetheless be unlatched under certain circumstances such as when excessive external shocks are applied to the HDD in many different directions or due to a “rebound-effect”. A rebound effect is generated when the actuator collides against a hook of the latch lever, the latch lever rebounds from the actuator arm, and the actuator arm collides with the hook again all due to the inertia of the latch lever and actuator arm.
Another type of latch mechanism includes a latch lever having a hook at a leading end thereof and a magnetic retract ball at a rear end thereof, and a bobbin protrusion which extends from a rear end portion of the actuator arm and which also includes a magnetic retract ball. The latching and unlatching of the actuator arm is controlled by the bobbin protrusion and the latch lever using the magnetic force between the retract balls and a magnet of the VCM. However, the size of the retract balls and the distances between the actuator arm, bobbin protrusion portion and the hook of the latch lever necessary to ensure the latching of the actuator arm while the read/write head is parked compromise the ability of the latch mechanism to unlatch the actuator arm when the HDD is to perform a read/write operation.